Various techniques are used to measure formation properties, such as transient electromagnetic (EM) measurement techniques. Transient EM methods such as deep transient logging while drilling (LWD), especially using “look-ahead” capability, have been shown to have great use in geologic formation evaluation and measurement. Transient EM techniques involve disposing a tool including at least one transmitter and receiver, and transmitting transient pulses of current into a formation. The induced electromagnetic field and decay responses are measured.
Various inversion techniques can be utilized to model earth formations based on measured TEM data. An ongoing challenge for transient EM techniques is the reduction of time required to perform inversion of the measured data, especially for techniques in which the inversion is performed in real time, such as during LWD operations. Numerical modeling of synthetic transient signals is time-consuming because, in many instances, synthetic time-dependent signals used for modeling must be calculated by inverse Fourier transform of frequency-dependent signals.